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[DebugInfo] Avoid LSR crash on large integer inputs 

Loop strength reduction tries to recover debug variable values by looking
for simple offsets from PHI values. In really extreme conditions there may
be an offset used that won't fit in an int64_t, hitting an APInt assertion.

This patch adds a regression test and adjusts the equivalent value
collecting code to filter out any values where the offset can't be
represented by an int64_t. This means that for very large integers with
very large offsets, the variable location will become undef, which is the
same behaviour as before 2a6782bb9f / D87494.

Differential Revision: https://reviews.llvm.org/D94016
This commit is contained in:
Jeremy Morse 2021-01-05 10:21:17 +00:00
parent 9ad83fd6dc
commit 914066fe38
2 changed files with 76 additions and 2 deletions
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5
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -5796,8 +5796,9 @@ static void DbgGatherEqualValues(Loop *L, ScalarEvolution &SE,
if (!SE.isSCEVable(Phi.getType()))
continue;
auto PhiSCEV = SE.getSCEV(&Phi);
if (Optional<APInt> Offset =
SE.computeConstantDifference(DbgValueSCEV, PhiSCEV))
Optional<APInt> Offset =
SE.computeConstantDifference(DbgValueSCEV, PhiSCEV);
if (Offset && Offset->getMinSignedBits() <= 64)
EqSet.emplace_back(std::make_tuple(
&Phi, Offset.getValue().getSExtValue(), DVI->getExpression()));
}

73
llvm/test/Transforms/LoopStrengthReduce/dbg-preserve-1.ll Normal file
View File

@ -0,0 +1,73 @@
; RUN: opt < %s -loop-reduce -S | FileCheck %s
;
; Test that LSR avoids crashing on very large integer inputs. It should
; discard the variable location by creating an undef dbg.value.
;
; CHECK: call void @llvm.dbg.value(metadata i128 undef,
source_filename = "<stdin>"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define dso_local void @qux() local_unnamed_addr !dbg !10 {
entry:
br label %for.body, !dbg !17
for.body: ; preds = %for.body.for.body_crit_edge, %entry
%0 = phi i128 [ 0, %entry ], [ %.pre8, %for.body.for.body_crit_edge ], !dbg !19
%add6.i.i = add i128 %0, 18446744073709551615, !dbg !35
call void @llvm.dbg.value(metadata i128 %add6.i.i, metadata !25, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 128)), !dbg !36
br label %for.body.for.body_crit_edge
for.body.for.body_crit_edge: ; preds = %for.body
%.pre8 = load i128, i128* undef, align 16, !dbg !19, !tbaa !37
br label %for.body, !dbg !17
}
; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!7, !8, !9}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, globals: !2, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "/tmp/beans.c", directory: "/tmp")
!2 = !{}
!3 = !{!4}
!4 = !DIDerivedType(tag: DW_TAG_typedef, name: "uint64_t", file: !5, line: 1, baseType: !6)
!5 = !DIFile(filename: "/tmp/beans.c", directory: "")
!6 = !DIBasicType(name: "long unsigned int", size: 64, encoding: DW_ATE_unsigned)
!7 = !{i32 7, !"Dwarf Version", i32 4}
!8 = !{i32 2, !"Debug Info Version", i32 3}
!9 = !{i32 1, !"wchar_size", i32 4}
!10 = distinct !DISubprogram(name: "qux", scope: !5, file: !5, line: 27, type: !11, scopeLine: 27, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!11 = !DISubroutineType(types: !12)
!12 = !{null, !13, !13}
!13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !14, size: 64)
!14 = !DIDerivedType(tag: DW_TAG_typedef, name: "croix", file: !5, line: 2, baseType: !15)
!15 = !DIDerivedType(tag: DW_TAG_typedef, name: "__uint128_t", file: !1, baseType: !16)
!16 = !DIBasicType(name: "unsigned __int128", size: 128, encoding: DW_ATE_unsigned)
!17 = !DILocation(line: 30, column: 3, scope: !18)
!18 = distinct !DILexicalBlock(scope: !10, file: !5, line: 30, column: 3)
!19 = !DILocation(line: 12, column: 25, scope: !20, inlinedAt: !30)
!20 = distinct !DISubprogram(name: "bar", scope: !5, file: !5, line: 8, type: !21, scopeLine: 8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !24)
!21 = !DISubroutineType(types: !22)
!22 = !{null, !23, !13}
!23 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !4, size: 64)
!24 = !{!25}
!25 = !DILocalVariable(name: "tmp", scope: !20, file: !5, line: 9, type: !26)
!26 = !DIDerivedType(tag: DW_TAG_typedef, name: "xyzzy", file: !5, line: 3, baseType: !27)
!27 = !DICompositeType(tag: DW_TAG_array_type, baseType: !14, size: 512, elements: !28)
!28 = !{!29}
!29 = !DISubrange(count: 4)
!30 = distinct !DILocation(line: 23, column: 3, scope: !31, inlinedAt: !32)
!31 = distinct !DISubprogram(name: "baz", scope: !5, file: !5, line: 21, type: !11, scopeLine: 21, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!32 = distinct !DILocation(line: 31, column: 5, scope: !33)
!33 = distinct !DILexicalBlock(scope: !34, file: !5, line: 30, column: 31)
!34 = distinct !DILexicalBlock(scope: !18, file: !5, line: 30, column: 3)
!35 = !DILocation(line: 12, column: 23, scope: !20, inlinedAt: !30)
!36 = !DILocation(line: 0, scope: !20, inlinedAt: !30)
!37 = !{!38, !38, i64 0}
!38 = !{!"__int128", !39, i64 0}
!39 = !{!"omnipotent char", !40, i64 0}
!40 = !{!"Simple C/C++ TBAA"}